A Thermal Elastohydrodynamic Inlet Zone Analysis

1975 ◽  
Vol 97 (2) ◽  
pp. 212-216 ◽  
Author(s):  
L. E. Murch ◽  
W. R. D. Wilson
Keyword(s):  
Film Thickness ◽  
Reynolds Equation ◽  
Substantial Reduction ◽  
Lubricant Film ◽  
Simple Equation ◽  
Viscous Heating ◽  
Style Analysis ◽  
Lubricant Film Thickness ◽  
Lubricated Contacts ◽  
Inlet Zone

An equation which takes account of the effects of viscous heating is used in place of the conventional Reynolds equation in a Grubin style analysis of the elastohydrodynamic inlet zone. The analysis indicates that viscous heating in the inlet zone can result in substantial reduction in the lubricant film thickness. The results of the analysis are expressed in a simple equation which will be useful for the design of elastohydrodynamically lubricated contacts under conditions where viscous heating is important.

The Effect of Porosity of Articular Cartilage on the Lubrication of a Normal Human Hip Joint

1992 ◽  
Vol 206 (3) ◽  
pp. 117-124 ◽  
Author(s):  
Z M Jin ◽  
D Dowson ◽  
J Fisher
Keyword(s):  
Articular Cartilage ◽  
Synovial Fluid ◽  
Film Thickness ◽  
Hip Joint ◽  
Elastic Material ◽  
Single Phase ◽  
Reynolds Equation ◽  
Lubricant Film ◽  
Lubricant Film Thickness ◽  
Normal Human

The effect of porosity of articular cartilage on the lubrication of a normal human hip joint has been studied. The poroelasticity equation of articular cartilage and the modified Reynolds equation for the synovial fluid lubricant have been successfully solved under squeezefilm motion and for the conditions experienced in a normal human hip joint. It has been shown that porosity of the articular cartilage depletes the lubricant film thickness, rather than increasing it, particularly when the lubricant film thickness becomes small. Furthermore, it has been shown that articular cartilage can be treated as a single-phase incompressible elastic material in the lubrication modelling under physiological walking conditions.

A Thermal Reynolds Equation and Its Application in the Analysis of Plasto-Hydrodynamic Inlet Zones

1974 ◽  
Vol 96 (4) ◽  
pp. 572-577 ◽  
Author(s):  
W. R. D. Wilson ◽  
S. M. Mahdavian
Keyword(s):  
Energy Dissipation ◽  
Film Thickness ◽  
Reynolds Equation ◽  
Wire Drawing ◽  
Lubricant Film ◽  
Pressure Gradients ◽  
Lubricant Film Thickness ◽  
Strip Rolling ◽  
Deformation Processes ◽  
Lubricated Contact

An equation which is equivalent to the steady, one-dimensional incompressible Reynolds equation but which takes account of viscosity variations across the lubricant film thickness due to energy dissipation within the film is developed. It indicates that the pressure gradients developed in a lubricated contact are reduced by the influence of energy dissipation. The use of the equation is illustrated by applying it in the analysis of the inlet zones of continuous deformation processes such as strip rolling and strip and wire drawing. The analysis indicates that thermal effects play an important role in deciding the lubricant film thickness in such contacts.

Study of Direct Measuring of Lubricant Condition in Rolling Element Bearings With Microcomputer Technique

1990 ◽  
Vol 112 (1) ◽  
pp. 92-97 ◽  
Author(s):  
Dongchu Zhao
Keyword(s):  
Film Thickness ◽  
Strain Gage ◽  
Lubricant Film ◽  
Rolling Element Bearings ◽  
Main Program ◽  
Test Apparatus ◽  
Lubricant Film Thickness ◽  
Rolling Element ◽  
Lubricant Films ◽  
Flow Charts

A method for measuring the lubricant condition with strain gage in rolling element bearings and the instrument used are introduced. In order to illustrate the method and the instrument, the theory of measuring lubricant films in rolling element bearings using strain technique, test apparatus, microcomputer hardware as well as software, flow charts for the main program and subprograms, are first described in detail. In addition, the lubricant film thickness is measured for several different lubricants and results are compared with theoretical ones. It is demonstrated that using the method and the instrument introduced in this paper, one can measure the lubricant condition inside bearings very accurately.

Optimized Mapping of Pressure in Lubricated Point Contacts Based on Measured Film Thickness

2007 ◽  
Author(s):  
Radek Polisˇcˇuk ◽  
Michal Vaverka ◽  
Martin Vrbka ◽  
Ivan Krˇupka ◽  
Martin Hartl
Keyword(s):  
Film Thickness ◽  
Numerical Solution ◽  
Point Contact ◽  
Contact Fatigue ◽  
Lubricant Film ◽  
Rolling Contact ◽  
Experimental Film ◽  
Lubricated Contacts ◽  
Practical Performance ◽  
Traction Drives

The surface topography plays significant role in lifetime of highly loaded machine parts with lubricated contacts. Many elements like gears, rolling bearings, cams and traction drives operate in mixed lubrication conditions, where the lubricant film behavior closely implies the main practical performance parameters such as friction wear, contact fatigue and scuffing. For prediction of wear and especially contact fatigue, the values and distribution of the pressure in rolling contact are often required. The usual theoretical approach based on numerical solution of physical-mathematical models built around the Reynolds equation can be extremely time consuming, especially when lubricant films are very thin, and contact load and required resolution very high. This study presents a further refined approach to our previously published experimental method, based on on inverse elasticity theory and fast convolution transformation between the lubricant film thickness map and the pressure distribution within the point contact. The experimental film thickness maps of EHD lubricated contacts with smooth and dented surfaces were processed using colorimetric interferometry and validated using numerical solution, in order to calibrate numerical parameters and to find limits of the new approach.

scholarly journals An investigation into the oil transport and starvation of piston ring pack

2018 ◽  
Vol 233 (1) ◽  
pp. 112-124 ◽  
Author(s):  
SR Bewsher ◽  
M Mohammadpour ◽  
H Rahnejat ◽  
G Offner ◽  
O Knaus
Keyword(s):  
Film Thickness ◽  
Boundary Conditions ◽  
Piston Ring ◽  
Gasoline Engine ◽  
Reverse Flow ◽  
Lubricant Film ◽  
Total Power ◽  
Lubricant Film Thickness ◽  
Piston Ring Pack ◽  
Ring Pack

In order to accurately predict the lubricant film thickness and generated friction in any tribological contact, it is important to determine appropriate boundary conditions, taking into account the oil availability and extent of starvation. This paper presents a two-dimensional hydrodynamic model of a piston ring pack for prediction of lubricant film thickness, friction and total power loss. The model takes into account starvation caused by reverse flow at the conjunctional inlet wedge, and applied to a ring pack, comprising a compression and scraper ring. Inlet boundaries are calculated for an engine cycle of a four-cylinder, four-stroke gasoline engine operating at 1500 r/min with conditions pertaining to the New European Drive Cycle. The analysis shows the two main sources of starvation: first, due to a physical lack of inlet meniscus and second, due to reverse flow at the inlet wedge significantly affecting the prevailing conditions from the generally assumed idealised boundary conditions. Such an approach has not hitherto been reported in literature.

Instrumented Engine Bearings for Lubricant Film Thickness Measurement

MTZ worldwide ◽  
2021 ◽  
Vol 83 (1) ◽  
pp. 28-37
Author(s):  
Henry Brunskill ◽  
Andrew Hunter ◽  
Hosung Nam ◽  
Junsik Park
Keyword(s):  
Film Thickness ◽  
Thickness Measurement ◽  
Lubricant Film ◽  
Lubricant Film Thickness ◽  
Film Thickness Measurement

Gear Tribology and Lubrication

2005 ◽  
pp. 19-38
Keyword(s):  
Film Thickness ◽  
Case History ◽  
Failure Modes ◽  
Gear Tooth ◽  
Lubricant Film ◽  
Flash Temperature ◽  
Lubricant Film Thickness ◽  
Film Lubrication

Abstract This chapter reviews the knowledge of the field of gear tribology and is intended for both gear designers and gear operators. Gear tooth failure modes are discussed with emphasis on lubrication-related failures. The chapter is concerned with gear tooth failures that are influenced by friction, lubrication, and wear. Equations for calculating lubricant film thickness, which determines whether the gears operate in the boundary, elastohydrodynamic, or full-film lubrication range, are given. Also, given is an equation for Blok's flash temperature, which is used for predicting the risk of scuffing. In addition, recommendations for lubricant selection, viscosity, and method of application are discussed. The chapter discusses in greater detail the applications of oil lubricant. Finally, a case history demonstrates how the tribological principles discussed in the chapter can be applied practically to avoid gear failure.

scholarly journals The Impact of Lubricant Film Thickness and Ball Bearings Failures

Lubricants ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 48 ◽  
Author(s):  
Matthew David Marko
Keyword(s):  
Film Thickness ◽  
Fatigue Failure ◽  
Failure Mechanisms ◽  
Roller Bearing ◽  
Lubricant Film ◽  
Theoretical Formula ◽  
Empirical Equations ◽  
Ball Bearings ◽  
Lubricant Film Thickness ◽  
The Impact

An effort was made to find a relationship between the lubricant thickness at the point of contact of rolling element ball bearings, and empirical equations to predict the life for bearings under constant motion. Two independent failure mechanisms were considered, fatigue failure and lubricant failure resulting in seizing of the roller bearing. A theoretical formula for both methods was established for the combined probability of failure using both failure mechanisms. Fatigue failure was modeled with the empirical equations of Lundberg and Palmgren and standardized in DIN/ISO281. The seizure failure, which this effort sought to investigate, was predicted using Greenwood and Williamson’s theories on surface roughness and asperities during lubricated contact. These two mechanisms were combined, and compared to predicted cycle lives of commercial roller bearing, and a clear correlation was demonstrated. This effort demonstrated that the Greenwood–Williams theories on the relative height of asperities versus lubricant film thickness can be used to predict the probability of a lubricant failure resulting in a roller bearing seizing during use.

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